1. Field of the Invention
The present invention relates to a ball-type check valve assembly adapted to be incorporated in strings of pipe, tubing and conduit to control the passage of fluids therethrough and, more particularly, relates to a ball-type check valve assembly particularly adapted to be incorporated in float shoes or float collars to control the passage of cement therethrough.
2. Prior Art
It is conventional practice in the oil and gas industry to cement casing in well bores in order to secure and support the casing in the well bore and to isolate various formations from one another by preventing migration of formation fluids up and down the well bore. Float equipment, such as float shoes and float collars, are typically utilized for this purpose. Such float equipment places the cement in the annulus between the casing and the well bore wall by conducting cement down the casing and out through the bottom thereof where it flows upwardly through the annular space between the casing and the bore hole wall to the desired level. During placement of the cement, it must pass through the equipment freely, but upon completion of the cementing process, the equipment must positively prevent backflow of the cement into the casing. The consequences of such float equipment not preventing backflow are always detrimental and costly. For example, leaking floating equipment allows the cement to set up inside the casing which thereby causes the need to drill it out. Even more serious consequences may result from lowering the cement level in the annulus, thus possibly exposing formations which are intended to be sealed off. Remedial work is very costly in direct expenses and consequential costs such as delay in completion or total loss of a well. The only way to prevent backflow through otherwise leaking float equipment is to hold pressure on the casing which in turn affects the quality of the cementing operation because when the cement has cured and the pressure on the casing is released, a leakage path results between the casing and the cement. Accordingly, it is necessary to provide a valve which will resist the back pressure of the cement slurry in the annulus upon completion of the cementing operation, and which is capable of withstanding the abrasive action of fluid passing through it at high flow rates and for long duration.
Although it has been proposed to use flapper valves and plunger valves in performing the above-identified functions, it has been found that such types of valves are subject to considerable wear because of the movable parts therein and are therefore not reliable for extended periods of use such as in deep wells where large quantities of cement are used and where large volumes of drilling fluid are circulated prior to cementing. For example, in the typical flapper valve assembly there is a flapper which is hinge suspended and spring operated. With high and extended flow-rates, the flappers become very unsteady thereby causing excessive wear to the flapper plate, the hinge mechanism and the spring and such excessive wear renders the flapper valve ineffective for preventing backflow. Likewise, the typical plunger valve assembly utilizes a spring mechanism which is susceptible to excessive wear caused by repeated movement of the plunger and plunger stem thereagainst. In addition, the wear on the plunger stem leads to misalignment of the plunger with the plunger seat which allows leakage of cement therethrough. Thus, plunger valves are also not reliable for use in deep wells. Due to the inadequacies of flapper valve assemblies and plunger valve assemblies, it has been determined that a ball-type check valve assembly is more suitable for preventing backflow of the cement.
Various ball-type check valve assemblies have been designed and manufactured for controlling the passage of fluids through pipes, conduits, tubings and the like. Examples of such ball-type float valve assemblies are disclosed in Harrison et al U.S. Pat. No. 4,529,167; Garneau U.S. Pat. No. 4,527,594; Vadasz U.S. Pat. No. 4,513,778; Sigworth, Jr. U.S. Pat. No. 4,314,667; Ninomiya et al U.S. Pat. No. 4,286,622; Clark, Jr. U.S. Pat. No. 3,096,825; Ecker U.S. Pat. No. 2,682,281; and Hudson U.S. Pat. No. 2,155,550.
A common characteristic of ordinary ball-type check valve assemblies is that the ball valve member is easily unseated from the ball valve member retainer and, as fluid continues to flow through the valve assembly, the ball valve member is subject to a considerable amount of random movement, hammering and peening. Such random movement, hammering and peening of the ball valve member inflicts appreciable damage to the check valve cage and to the ball valve seats, as well as to the ball valve member itself, such damage thereby rendering the apparatus ineffective for controlling the passage of fluids therethrough.
Prior art ball-type check valve assemblies have proved to be unsatisfactory for positively supporting and stabilizing the ball valve member to reduce or eliminate such random movement, hammering and peening of the ball valve member.